Sliding devices are already known which use sliding screws to open and/or close chucks and so on. The sliding screw is conventionally needed to make smaller in the outside diameter at an axial end thereof than in the major zone of the sliding screw to mate with a nut. With the prior sliding devices constructed as stated earlier, the angular-contact bearings are thrust directly with the coupling ends. A separate collar is used around the outside diameter of the axial end of the sliding screw to fasten the angular bearing. Conventionally, there has been an issue that the collar and the end of the angular-contact bearing slide each other after the torque of the motor have become large. Moreover, there is known another type of the sliding device in which a collar integral with a flange is used after a nut is mated with the lead screw. The sliding device of the type as recited just earlier has been troublesome because press-fitting, adhesion and so on have been needed for fixing. With the sliding device of the type as recited just earlier, the lead screw at the axial end thereof has to be also made less in outside diameter as in the former sliding device to mate with a nut. With the prior sliding devices constructed as described earlier, thus, it is needed to select a unique angular-contact bearing less in inside diameter for supporting rotation. Moreover, the coupling end is to be made the size or dimension different from the diameter of the motor shaft. Thus, the prior sliding devices constructed as described earlier, as making it tough to use any universal parts or components, requires producing unique parts. This will cause a serious issue of increase of production cost.
One version of the prior small-sized sliding devices made further smaller in lengthwise direction is disclosed in the commonly assigned Japanese Patent No. 5 047 749, in which a motor is actuated to rotate a lead screw to move a slide table in an axial direction of a guide rail. The lead screw has chucks and a bearing is interposed between the chucks and a coupling member. With the sliding device constructed as stated earlier, there is no use of bearing nut, but a collar integral with a stepped flange is made integral with the lead screw. Nevertheless, the sliding device constructed as recited just earlier has been troublesome because adhesion on top of press-fitting has been needed for fixing.
With the sliding device constructed as recited just earlier, the coupling member instead of using the bearing nut to fix the angular-contact bearing is directly assembled to make less the overall length of the table. It will be said that the nut incorporated in the table is only a linear motion guide unit, namely a single type. Then, a small-sized sliding device has been proposed in which a pair of sliders or tables is mounted on a lead screw for sliding movement along the lead screw in such a way coming closer and/or away from each other to transfer any part or component while gripping the part between the tables.